Among the policies NASCAR is considering is whether to require baseline testing for drivers prior to the season, like the IndyCar Series and other sports leagues.

Earnhardt revealed last week that he suffered a concussion in an Aug. 29 crash during a test session at Kansas Speedway. He admitted that he continued to race despite not feeling well, and then suffered another concussion in a last-lap wreck at Talladega Superspeedway Oct. 7.

After seeing a doctor in Charlotte on Oct. 9-10, Earnhardt was not cleared to return to racing and missed Saturday’s race at Charlotte Motor Speedway. He also is expected to miss Sunday’s race at Kansas Speedway as he continues to recover.

With baseline testing, if a driver suffers a head injury, a follow-up test could determine the seriousness of an injury.

“We are always evaluating and reviewing our policies and procedures, especially when it comes to safety,'' NASCAR spokesman Kerry Tharp said. "We will continue to work closely and review our policies with the medical experts that advise NASCAR on baseline testing and other medical issues.

"While not mandatory, baseline testing can and has been used and is just one of the many tools a neurologist or neurosurgeon may use as part of a neurological assessment.''

After being diagnosed with a concussion, Earnhardt visited noted concussion expert Dr. Michael Collins of the University of Pittsburgh Medical Center Sports Concussion Program.

Collins helped design the baseline test that is used by various sports leagues, including the IndyCar Series.

Drivers in that series must have the Collins-developed ImPACT test—Immediate Postconcussion Assessment and Cognitive Testing—before they compete in the series and then at least once every two years. The 20-minute test measures a range of neurocognitive functions, including memory, reaction time, attention span, and other cognitive abilities, according to IndyCar.

If a driver suffers a head injury, doctors perform the test again to determine the severity.

“The ImPACT test allows us to measure cognitive functions like reaction time, thinking ability, reasoning ability and memory—things that we otherwise don’t really have tools for measure,” said IndyCar Director of Medical Services Dr. Mike Olinger.

Earnhardt had an ImPACT test done last week but didn’t have one prior to his two accidents this season.

“Some of the testing that's done like the ImPACT tests that Dale had, those are tests that we can follow, and if he should have an injury again in the future, we can use that as a baseline,” said neurosurgeon Dr. Jerry Petty, Earnhardt’s doctor. “What we'd want to make sure is that baseline doesn't start to fall off and even fall off without being tested.”

Former Sprint Cup driver Steve Park, who suffered a serious head injury in a Nationwide Series crash at Darlington Raceway in 2001, has been a longtime advocate of baseline testing.

Park took the ImPACT baseline test in 2003 after suffering a second concussion. But because he didn’t take it after his first injury, doctors were not able to determine the full extent of his injury.

Park dropped out of the Sprint Cup Series after struggling in 2002-03 and has raced only occasionally in NASCAR’s lower series the past few years.

"I am a big proponent in NASCAR that the ImPACT test, if it was part of your physical exam as a driver and you had it at the liaison office at every track, if you did get hurt during testing, qualifying or practice you could easily take the test (again) in 20 or 30 minutes and they could have a competent evaluation if you're hurt or not,'' Park told ESPN.com.

Richard Childress Racing started having its drivers take a baseline test a couple of years ago, driver Kevin Harvick said.

“I know for us at RCR, we already have baseline scans we put in place a couple years ago,” Harvick said. “We have some things that (team owner) Richard (Childress) has made us put in place already.

“It's just a matter of what the team does, how it's supposed to be structured, how far you want to take it. It's a fine balance. I think, obviously, when Dale Jr. has a situation like this, everybody's looking at it a little bit differently than they have in the past.”

Some drivers believe such testing should be left up to the individual drivers and teams and not required by NASCAR.

After Harvick made his statement, Brad Keselowski tweeted: “Good, let the teams handle this. The sport is plenty regulated as is.”

Earnhardt crashed during an Aug. 29 tire test at Kansas, a crash that he said registered 40 Gs. He was seen by a doctor in the back of an ambulance, released and cleared to return to racing. He complained of headaches to his team but decided to fight through the pain and keep racing.

About six weeks later, on Oct. 7, he was involved in a 24-car crash on the final lap at Talladega, where his car was spun around. Earnhardt didn’t have to go to the infield medical center because he drove his car across the finish line and back to the garage. After a few days of persistent headaches, Earnhardt went to a doctor, was diagnosed with the concussion and told by Dr. Petty, who also is a NASCAR consultant, that he could not race for at least two weeks.

Baseline testing is regulated in IndyCar but it’s not like it can be done weekly, Olinger said, so the series must rely on drives to let IndyCar officials know if they’re suffering symptoms. IndyCar also uses the NFL Sideline Concussion Assessment Tool, a cognitive test that takes up to eight minutes.

“I don’t know how you can police it more careful than that—we can’t do an assessment with every driver before every event,” Olinger said. “We don’t have the resources to do that and the drivers don’t really have the time to come in and spend the time with us (on race day).”

Olinger said the circuit’s traveling safety team talks to drivers and observes them after an accident, asking the driver questions to see if they have any loss of memory or loss of consciousness. They also observe how the driver acts and walks over to the safety vehicle to determine whether they need additional testing.

Even at a test, while the IndyCar medical team is not there, it will have one of its traveling doctors present.

“Any time there is a crash, they respond to the crash and they do an assessment of the driver,” Olinger said. “If they have any suspicions that the driver sustained a concussion, then they would recommend that he not drive and follow up with us prior to resume driving.”

NASCAR doesn’t have a traveling safety team but does have medical liaisons that know a driver’s medical history.

“If a driver were to have an incident, first and foremost (he) is evaluated in the infield care center where we've got board certified emergency technicians and doctors,” NASCAR vice president of operations Steve O’Donnell said last week. “And they'll evaluate the driver at that point.

“If the driver complains of any symptoms or if the emergency room physician believes there may be symptoms, we refer them to a neurologist.”